This is what scientists say: climate change is coming earlier and stronger than expected

The United in Science report brings together details on the current state of the climate and presents trends in atmospheric emissions and concentrations of major greenhouse gases.

In the research, scientists highlight the urgency of a fundamental socio-economic transformation in key sectors such as land use and energy to avoid a dangerous increase in global temperature with potentially irreversible impacts. They also examine tools to support both mitigation and adaptation.

What is the situation according to scientists?

The global climate

The average global temperature for 2015-2019 is on track to be the warmest of any equivalent period on record. It is currently estimated at 1.1°C, one degree above pre-industrial times (1850–1900).

Heat waves in recent years have been the deadliest, affecting every continent and setting record temperature records nationwide.

Widespread and long-lasting heat waves, record fires and other devastating events such as tropical cyclones, floods and drought have had a major impact on socio-economic development and the environment.

Unprecedented fires

The summer of 2019 saw unprecedented fires in the Arctic that in June alone emitted 50 megatons of carbon into the atmosphere. This is more than all the fires put together in that region from 2010 to 2018. There were also multiple fires in the Amazon rainforest in particular in August.

Devastating cyclones

The world’s biggest economic losses have been linked to tropical cyclones. The 2018 season was especially active, with the highest number of tropical storms of any year in the 21st century.

All basins in the Northern Hemisphere experienced higher-than-normal activity. The Northeast Pacific recorded its highest Cyclone Energy Value in its history.

The 2017 Atlantic hurricane season was one of the most devastating in history with more than $125 billion in losses associated with Hurricane Harvey alone. Unprecedented consecutive tropical cyclones from the Indian Ocean hit Mozambique in March and April 2019.

Continued decline in sea ice and ice mass

Arctic summer sea ice extent has declined at a rate of about 12% per decade during 1979-2018. In addition, the four lowest values for winter sea ice extent occurred between 2015 and 2019.

The picture is similar to the other pole. The amount of ice lost annually from the Antarctic layer increased at least sixfold between 1979 and 2017 and the loss of glacier mass for 2015-2019 is the highest in any five-year period on record.

Sea level rise is accelerating, seawater is becoming more acidic

The observed rate of global mean sea level rise accelerated from 3.04 millimeters per year during the period 1997–2006 to approximately 4mm during the period 2007–2016.

This is due to the higher rate of warming and melting of the Greenland and West Antarctic ice sheets. In addition, there has been an overall 26% increase in ocean acidity since the beginning of the industrial age.

Drought that causes hunger

According to the Food and Agriculture Organization of the United Nations, extreme weather situations are among the main drivers of recent increases in global hunger after a decline for several years.

The frequency of drought conditions from 2015 to 2017 show the impact of the El Niño phenomenon in 2015 to 2016 on crops. Wide areas of Africa, Central America, Brazil and the Caribbean, as well as Australia experienced a large increase in the frequency of drought conditions between 2015 and 2017 compared to the last 14 years.

More climate deaths

According to the World Health Organization between 2000 and 2016 the number of people exposed to heat waves has increased by around 125 million. The average length of individual heatwave events was 0.37 days longer, compared to the period between 1986 and 2008, contributing to an increased risk of heat-related illness or death.

Record greenhouse gas concentrations in the atmosphere

Levels of the main long-lived greenhouse gases, carbon dioxide (_CO2), methane (_CH4) and nitrous oxide (_N2O) have reached record levels.

The last time Earth’s atmosphere contained 400 parts per million of _CO2 it was about 3 to 5 million years ago, when the global average surface temperature was 2 to 3 degrees warmer than today, the ice sheets in Greenland and West Antarctica melted, and parts of the East Antarctic ice fell, all of which caused a global sea level rise of 10 to 20 meters compared to today.

In 2018, the global _co2 concentration was 407.8 parts per million (ppm), 2.2 ppm more than in 2017. Preliminary data from a set of greenhouse gas monitoring sites for 2019 indicate that carbon dioxide concentrations are on track to reach or even exceed 410 parts per million by the end of 2019.

In 2017, globally averaged atmospheric concentrations have reached nearly triple pre-industrial levels.

In addition, the average growth rate of carbon dioxide over three consecutive decades (1985–1995, 1995–2005, and 2005–2015) increased from 1.42 ppm per year, to 1.86 ppm and then to 2.06 ppm.

Carbon emissions

Carbon dioxide emissions grew by 2% and reached a record 37 billion tons in 2018. So far there is no sign that there will be a record this year.

Current economic and energy trends suggest that emissions will be at least as high in 2019 as in 2018. Global GDP is expected to grow at 3.2% in 2019, and if the global economy decarbonizes at the same rate as in the past 10 years, that would still lead to an increase in global emissions.

Despite the extraordinary growth of renewable fuels over the past decade, the global energy system is still dominated by fossil fuel sources. The annual increase in global energy use is greater than the increase in renewable energy, which means that the use of fossil fuels continues to grow. “This growth needs to stop immediately,” the scientists say.

The net-zero emissions needed to stabilize the climate require both an acceleration in the use of non-carbon energy sources and a rapid decline in fossil fuels in the energy industry. “This dual requirement represents a challenge,” the report says.

Natural carbon dioxide sinks, such as vegetation and oceans, which remove about half of all emissions from human activities, will be less efficient in doing so. This underscores the need to reduce deforestation and expand natural _CO2 sinks, particularly those in forests and soils that can be improved through better habitat management and restoration.

The emissions gap, according to UN Environment

The United Nations Environment Programme’s Emissions Gap Reports, with the tenth edition to be published in November, assess the latest scientific studies on estimated current and future greenhouse gas emissions and compare them with the emission levels allowed for the world to progress towards the goals of the Paris Agreement.

This difference between “where we are likely to be and where we need to be” is known as the emissions gap.

Global emissions will not peak for 2020 and 2030 if current climate policies and Nationally Determined Contributions (NDCs) ambition levels are maintained. However, preliminary results from the 2019 Emissions Gap Report indicate that emissions gap continued to rise in 2018.

The level of ambition of countries’ Determined Contributions should roughly triple to align with the 2-degree limit set by the Paris Agreement and should be increased by about five times to align with the 1.5-degree limit.

If ambitions are not immediately increased and backed up with actions, you can no longer avoid exceeding that goal. If the emissions gap is not closed by 2030, it is quite possible that the target of a temperature increase well below 2 degrees will also be out of reach.

A substantial part of the technical potential can be achieved by scaling up and replicating existing and well-tested policies, such as the shift to renewable energy and reforestation, which simultaneously contribute to the key sustainable development goals.

The warnings of the Intergovernmental Panel on Climate Change

Three special reports published in 2018 and 2019 assess complementary and specific aspects of climate change, ahead of the sixth assessment report.

The Special Report on Global Warming of 1.5 degrees states that limiting warming to that increase is not physically impossible, but would require unprecedented transitions in all aspects of society. There are clear benefits of keeping warming at 1.5 degrees compared to 2 or more.

Every degree matters: limiting the increase can go hand in hand with achieving other global goals such as achieving sustainable development and eradicating poverty.

The Special Report on Climate Change and the Earth emphasized that soils are under increasing human pressure and that climate change adds to these pressures. At the same time, keeping global warming well below 2 degrees can only be achieved by reducing greenhouse gas emissions from all sectors, including land and food.

Research shows that better land management can contribute to tackling climate change, but land is not the only solution: reducing greenhouse gas emissions from all sectors, including energy, is essential to keeping global warming as close to 1.5 degrees as possible.

On 25 September 2019, the Intergovernmental Panel on Climate Change publishes the Special Report on the Ocean and cryosphere in a Changing Climate.

Towards the future

Consolidated evidence reinforces human influence as the dominant cause of changes in the Earth system, in a new geological epoch, the Anthropocene.

Increasing climate impacts increase the risks of crossing critical tipping points. They refer to thresholds that, if crossed, lead to far-reaching, in some cases abrupt and or irreversible changes, the research states.

There is a growing recognition that climate impacts are hitting harder and sooner than climate assessments indicated even a decade ago.

As climate change intensifies, cities are particularly vulnerable to impacts such as heat stress and can play a key role in reducing emissions locally and globally.

Strategies for mitigation and to improve adaptive risk management are needed in the future.

“Only immediate and comprehensive action encompassing: deep decarbonization complemented by ambitious policy measures, protection and enhancement of carbon sinks and biodiversity, and efforts to remove _CO2 from the atmosphere, will allow us to comply with the Paris Agreement,” the scientists say.

Source: United Nations